MySQL Set AutoReconnect

[Edlueze]

How to I set ‘autoReconnect=true’ in my KNIME DB Connector?

I recently set up a new machine with KNIME 4.1.1 and MySQL 8.0.19, then upgraded an old workflow with new DB Connectors and DB Writers. If I leave my workflow for 12 hours overnight then I run into the following error:

ERROR DB Writer 0:191:2825 Execute failed: The last packet successfully received from the server was 47,112,375 milliseconds ago. The last packet sent successfully to the server was 47,112,376 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.

I’m now trying to follow the recommendation to set the Connector/J connection property ‘autoReconnect=true’, but how? There seems to be three possible places in the DB Connector to set this. See the attached screenshots:

I found an old KNIME post from 2014 describing a similar problem and concluding that this setting was no help - that the problem could only be fixed on the MySQL server side:

Critical Problem with the DB Reader Node (2.9.0 - 2.9.2) @ MYSQL JDBC

Dear Knimers, I encountered a problem with the DB Reader recently. It does not occur very often and it is quite hard to track, but when it occurs, it breaks my production jobs. This is the thing: One of our batch jobs needs to read in 4 Tables from the MySQL Database of ours. The first and the second of these Tables are quite large (The queries return about 20 Million rows x 15 columns). From time to time, the second Database Reader Node fails on doing that with an error message like  "ERROR  …

Is that still true?

[mareike.hoeger]

Hi @Edlueze,
yes it looks like you have to change the wait_timeout setting on the server site.
Also MySQL does not recommend the usage of autoReconnect.

best regards Mareike